1. Technical Field
The present invention relates to an electronic device, an electronic apparatus, and a method of manufacturing an electronic device, and more particularly to an electronic device which has a cavity.
2. Related Art
An electronic device containing a function element produced by using MEMS (micro electro mechanical systems) technology is known, which element is disposed within a cavity on a substrate. The function element such as a micro vibrator and a micro sensor has a small structure which vibrates, deforms, or performs other actions. The pressure within the cavity is reduced so that the function element can easily operate.
The method of producing the cavity is disclosed in JP-A-2009-105411. According to the method shown in this reference, an interlayer insulation film is initially formed on an MEMS structure prepared on a substrate. Then, a first covering layer having through holes is so formed as to cover the interlayer insulation film around the MEMS structure. After formation of the first covering layer, etchant is introduced through the through holes of the first covering layer to remove the interlayer insulation film and make a movable unit of the MEMS structure movable. Finally, the through holes of the first covering layer are covered with a second covering layer so as to produce a closed cavity around the MEMS structure. The first covering layer is hereinafter referred to as a covering portion.
In case of the MEMS structure which is electrically driven, the covering portion provided thereon is made of material having electric conductivity so as to prevent entrance of electromagnetic wave noise into the cavity. In this case, wires connected with the MEMS structure needs to be insulated from the covering portion so as to allow extraction of electric signals to the outside of the covering portion.
When an interlayer insulation film is disposed between the wires and the covering portion, this interlayer insulation film is dissolved by etchant. In this case, the etchant having dissolved the interlayer insulation film flows toward the area around the covering portion, which may damage components disposed around the covering portion. For example, when an interlayer insulation film is provided around the covering portion, the enchant damages this interlayer insulation film around the covering portion. As a result, the strength of the covering portion lowers to such a degree that the cavity is difficult to be maintained. Accordingly, such an electronic device which can prevent flow of enchant to the outside of the covering portion has been demanded.